His architectural legacy includes countless monuments and over one thousand private villas.
After the Iranian Revolution he moved to Vancouver and lived in exile until his death.
Seyhoon became famous for his design work in the 1950s in Iran, including: Tehran's Central Railway Station and tombs of scientific/literary figures (such as the Avicenna Mausoleum in Hamadan).
He has been a faculty member of Tehran University's College of Architecture, where he also served as Dean of the College of Fine Arts (Beaux arts) of Tehran University for six years.